Method and device for production of hollow sections

ABSTRACT

The invention relates to a method and device used to produce hollow sections with very high degrees of reduction at very high manufacturing speeds, while at the same time maintaining or improving the quality of the final product. According to the inventive method, it is possible to produce hollow sections having defined cross-sectional forms and dimensions from a starting material in the form of hollow sections having larger diameters. The starting material is shaped to form the desired hollow section by combinations of stretch reductions and drawing through drawing nozzles. The invention also includes a device for carrying out the above-mentioned method.

[0001] The present invention relates to a method and a device for producing hollow profiled sections having defined cross-sectional shapes and dimensions, from a base material that is present in the form of hollow profiled sections with greater diameters.

[0002] Methods and devices for producing hollow profiled sections of the specified type are commonly known in the prior art.

[0003] The base material is present either in bar form or, wound on a roller, in the form of a so-called spool or coil. The process of reducing these types of base materials by drawing them to a desired diameter is known in the art. The disadvantage of the pure drawing processes is that comparatively high pulling forces must be employed, and thus even slightly damaged areas in the base material can result in tears. Furthermore, only average speeds can be realized. Moreover, depending upon the quality of the base material, it can be difficult to achieve improved centricity in the hollow profiled section.

[0004] Also known is the process of subjecting the base material that is present in bar or coil form to a stretch-reduction process in sets of rollers.

[0005] Known high-reduction processes that use a drawing block have the disadvantage that the material is bent during the drawing process, and as a result of the crushing of the inside wall or the pulling on the outside wall, uneven sides are produced.

[0006] Proceeding from the known state of the art, the objective of the invention is to provide a process and an apparatus with which in the production of hollow profiled sections of the described type very high reduction levels can be realized at high finishing speeds, while the quality of the final product is retained or improved.

[0007] For the technical achievement of this objective, in terms of the process, the invention proposes a process for producing hollow profiled sections having defined cross-sectional shapes and dimensions from base material in the form of hollow profiled sections with greater diameters, wherein the base material is formed via combinations of stretch-reduction and drawing through drawing plates to form the desired finished profile.

[0008] The method specified in the invention provides for the combination of stretch-reduction and drawing. This results in the particular advantage that, with the proper combination of these manufacturing processes, drawing and pressure forces to be applied to the material can be adjusted. Thus a stretch-reduction stage positioned in front of a drawing plate can cause the material to essentially be pushed through the plate. When this is combined with an additional stretch-reduction stage, an evening out is accomplished in the forming area. The use of stretch-reduction stages permits an extremely high, nearly unlimited reduction, since any irregularities in the profiled section resulting from the stretch-reduction process can be calibrated in a subsequent drawing process. This applies especially to the centricity of the hollow profiled section. It is proposed that the described forming combinations of stretch-reduction and drawing, which can be combined in nearly any possible sequence, be followed by thermal treatments for a process annealing of the material. For this, in terms of the apparatus, a furnace, especially an induction furnace with a connected cooling area, for example one that employs water, is proposed.

[0009] Pursuant to a further advantageous proposal, the formed material is post-formed following the temperature processing. Especially suited for this are stretch-reduction stations that correct only dimensional deviations. A purposeful post-reduction can, however, also be generated in this area. Additional combinations of stretch-reduction and drawing are also within the scope of the invention here.

[0010] Once this processing is complete, the hollow profiled section can be tested using customary methods, and cut into lengths or wound as a coil, and otherwise processed in the usual manner.

[0011] The process specified in the invention permits extreme reductions at very high speeds, which can reach 1,000 m/min and more. In this manner, with the combination of stretch-reduction and drawing specified in the invention, tears in the material resulting from slightly damaged areas in the base material can be prevented, and the quality of the final product can be substantially improved.

[0012] In terms of the apparatus, the invention proposes a device for producing hollow profiled sections having defined cross-sectional forms and dimensions from base material in the form of hollow profiled sections with greater diameters, characterized by at least one roller assembly for performing a stretch-reduction and at least one drawing plate assembly.

[0013] In an advantageous manner, rollers are positioned in pairs in the stretch-reduction stage that have the appropriate reduction passage. The subsequent roller pair is then positioned with rollers arranged at an angle to the previous roller pair. Thus, 90° angles, and any other intermediate angles, can be set. The base material then passes through the series of different pairs of rollers and is stretch-reduced in its cross-section.

[0014] Thus, any shapes, including semicircular, oval, rectangular, and so forth, can be advantageously produced with the invention. Even profiled tubes and, by combining the drawing plate with an inside tool, inner profilings, interior scoring, and so forth can be generated.

[0015] Pursuant to one advantageous proposal of the invention, the forming stage is equipped with a roller assembly, a drawing plate, and a subsequent roller assembly, connected in sequence. This results in a particularly advantageous distribution of drawing and pressure forces. The base material is drawn into the first roller assembly, which pushes it into the drawing plate, while the roller assembly positioned behind the drawing plate draws the material through the drawing plate. This results in the particularly high quality level in the area of the drawing plate, and in improved centricity.

[0016] In a stress-relieving stage an annealing furnace, preferably an induction furnace, and a cooling station, preferably one that employs water, are provided.

[0017] A further forming process, for example in the form of stretch-reduction roller assemblies, can advantageously be carried out subsequent to the temperature processing stage, in order to perform special shaping, finishing operations, and so forth.

[0018] Pursuant to one proposal of the invention, the device is equipped with a cutting machine with a discharge unit, so that lengths of hollow profiled bars that have been cut into sections can be ejected from the device.

[0019] The invention produces the advantage that at very high speeds, extreme reductions can be generated with a low risk of tearing. Furthermore, a very high quality, especially with respect to centricity and material surface, but also with respect to variability, can be generated. Thus any alternative forms including round, half-round, oval, rectangular, contours, inner scoring, and so forth can be formed.

[0020] The advantage of the assembly consists in the use of interior tools, so-called floating stoppers, which can be implemented individually ahead of the drawing plate or in different, sequential plates as a chain. With the use of conical, floating stoppers, precise inner diameters of the hollow profiled sections to be drawn can be created.

[0021] Additional advantages and characterizing features of the invention are disclosed in the following description with reference to the drawings, which show:

[0022]FIG. 1 a schematic view of sequential processing stations intended to illustrate the process and

[0023]FIG. 2 a frontal view of an exemplary design of a suitable device.

[0024] With the overall assembly shown in FIG. 1, at the start is a support bed for the base material in bar form 1, or a support for coils wound with base material 2. Whether it is present as bars or rolling off a coil, the material to be formed is fed to a first milling or rolling station 3, where it runs through sequential pairs of rollers, which between them form the shaped cross-section. These rollers are wholly or partially actuated and exert forces of pressure on the material to be shaped that serve to reduce the material. The material is then pushed into a drawing plate 4, in order to run through a subsequent set of rollers 5 designed to perform further stretch-reductions. From the drawing plate, then, the material in front of the plate is pushed forward by the first set of rollers 3, and the material behind the plate is drawn by the second set of rollers 5, so that in the drawing plate a distribution of force with respect to drawing/pressure is established.

[0025] An annealing furnace, for example an induction furnace, is indicated by the number 6, and a cooling stage, for example one that employs water, is indicated by the number 7.

[0026] The number 8 indicates an additional set of rollers or coils for performing a stretch-reduction either for additional shaping or for remachining.

[0027] A testing device 9, examines the material quality of the formed hollow profiled section, for example by means of eddy current measurements. Number 10 indicates a cutting assembly, which preferably is also equipped with a discharge unit designed to push material that has been cut into lengths out of the forming station. This material is then either wound via a conveyor belt 11 on a coil positioned on the station 12, or fed in the form of bar material to bar hoppers 16 by means of cross-transfer 14 via a conveyor belt 15.

[0028] Material that is determined by the testing device 9 to be defective is automatically transferred to the scrap hopper 13.

[0029] In accordance with FIG. 2 the device, shown here in a frontal view, i.e. in the direction of feed of the material to be processed, is comprised of a basic frame, which bears the entire assembly. The machine frame is indicated by the number 20. Two drive motors 21, 22 are connected to the roller pairs 25, 26 by means of transmissions 23, 24, allowing said rollers to be actuated. Appropriate assemblies are positioned one behind another in the plane of the drawing to form a stretch-reducing/forming stage, to which a drawing plate is connected and corresponding stretch-reducing/forming stations can be arranged one behind another.

[0030] The exemplary designs described serve only descriptive purposes and are not to be considered limitations of the invention.

[0031] Legend

[0032]1 Bar Loading Station

[0033]2 Coil Mount

[0034]3 Roller Pair

[0035]4 Drawing Plate

[0036]5 Roller Pair

[0037]6 Annealing Furnace

[0038]7 Cooling Stage

[0039]8 Roller Pair

[0040]9 Testing Device

[0041]10 Cutter

[0042]11 Conveyor Belt

[0043]12 Coil Mount

[0044]13 Scrap Hopper

[0045]14 Cross Transfer

[0046]15 Belt

[0047]16 Bar Hopper

[0048]20 Machine Frame

[0049]21 Motor

[0050]22 Motor

[0051]23 Transmission

[0052]24 Transmission

[0053]25 Roller Pair

[0054]26 Roller Pair 

1. Method for producing hollow profiled sections having defined cross-sectional forms and dimensions from base material in the form of hollow profiled sections with greater diameters, comprising: forming the base material is into the desired hollow profiled section via combinations of stretch-reduction and drawing through drawing plates.
 2. Method pursuant to claim 1, wherein the base material is formed via a combination of stretch-reduction, drawing, and subsequent stretch reduction.
 3. Method pursuant to claim 2, wherein an interior of the stretch-reduced hollow profiled section is calibrated in a drawing stage.
 4. Method pursuant to claims 1 wherein the hollow profiled section is stretch-reduced in a milling stage.
 5. Method pursuant to claim 1 after the forming process, the hollow profiled section is subjected to stress relief by means of heating.
 6. Method pursuant to claim 5, wherein the hollow profiled section is cooled following the stress-relief.
 7. Method pursuant to Claim 6, wherein the hollow profiled section is post-formed following the temperature treatment.
 8. Method pursuant to claim 7, wherein the post-forming is accomplished via stretch-reduction.
 9. Method pursuant to claim 1, wherein the finished hollow profiled section is cut into lengths.
 10. Device for producing hollow profiled sections having defined cross-sectional forms and dimensions from base material in the form of hollow profiled sections with greater diameters, comprising at least one roller assembly for performing a stretch-reduction and at least one drawing plate assembly.
 11. Device pursuant to claim 10, wherein rollers in each roller assembly are arranged in pairs, each with essentially parallel axes of rotation.
 12. Device pursuant to claim 11, wherein the axes of rotation of the roller pairs are arranged alternating at an angle of 90°, one above the other.
 13. Device pursuant to Claim 10, further comprising an interior tool inserted into the hollow profiled section at the drawing plate.
 14. Device pursuant to Claim 10, further comprising a post-forming stage 1 equipped with a drawing plate the at least one drawing plate assembly arranged between two roller units of the at least one roller assembly for the purpose of executing a the stretch-reduction.
 15. Device pursuant to Claim 10, further comprising an annealing furnace arranged to follow the post-forming stage.
 16. Device pursuant to claim 15, further comprising a cooling stage Positioned behind the annealing furnace.
 17. Device pursuant to Claim 16, further comprising a roller assembly is positioned to follow temperature processing station in the form of the annealing furnace and/or the cooling stage.
 18. Device pursuant to Claims 10, further comprising a cutter with a discharge unit. 